The present invention relates to a recording apparatus of the type that a visible image is first formed with image visualizing substance on a recording sheet and then heated to be fixed thereon.
A fixing unit for use with the recording apparatus of this type generally employs a roller fixing method whereby a transfer sheet formed thereon an unfixed toner image is heated during the transportation by being squeezed between a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer thereon for pressing the heating roller. The heating roller, however, is required to be maintained at an optimum temperature so as to avoid a so-called offset phenomenon that toner is transferred onto the heating roller, necessitating a large heat capacity of the heating roller or its heating element. It has therefore been necessary to set the heating roller at an optimum temperature by supplying electric power to the heating element for a predetermined period in advance of using it.
The print speed of recent recording apparatus such as a printer has become high. In order to cope with such high print speed, the heat capacity of the heating roller or its heating element has been determined in such a manner that electric power is supplied to the heating element at the same time upon reception of a record start instruction to thereby obtain an optimum fixing temperature when a transfer sheet reaches the fixing unit.
With such temperature control, electric power is supplied to the heating element irrespective of whether or not a toner image has been transferred to a transfer sheet. For example, even in the case where a controller unit outputs a "new page" code to feed a blank transfer sheet without any toner, electric power is supplied for the setting of the optimum fixing temperature, thereby consuming wasteful electric power.